For over four decades, extruded thermoplastic or elastomeric foam articles have been manufactured and distributed for a wide variety of uses. Over the years, numerous additional end products have benefitted from foamed thermoplastic or elastomeric members. Typical applications and fields in which such products have received substantial use and distribution include toys, furniture, beddings, packaging, shock absorption, construction, agriculture, insulation, and recreation.
In developing additional markets for foamed thermoplastic and elastomeric members, the practice of reducing the density of the polymer resin to produce a foamed article having a low density has received increasing attention. Presently, thermoplastic or elastomeric foams are categorized as either high or low density foam and are divided at approximately 240 kg/m.sup.3 (15 lbs/ft.sup.3).
Many favorable advantages are attained by reducing the density of the foamed products. Typically, these favorable properties include an increase in insulation value, an increase in flexibility of the product, cost reduction, higher resiliency, and increased rates of production. Unfortunately, some desirable properties are sacrificed with density reduction, such as a reduction in mechanical properties of the resulting product. Typically, mechanical properties are reduced at an approximate rate proportional to one over the density reduction squared. In order to overcome the reduction in mechanical properties, many applications employ a combination of different materials having different densities, attempting to produce a resulting product which will possess the desired physical characteristics.
Typically, thermoplastic or elastomeric members of this nature which incorporate a plurality of different materials of different densities are produced by coextrusion or cross-head extrusion. By employing either of these processes, two or more distinct layers are combined in a single, or multi-step extrusion operation to produce a final product having separate and distinct layers of varying material compositions and/or material densities. These distinct layers may or may no possess integrally bonded interfaces.
The principal distinction between co-extrusion and cross-head extrusion is the number of operations required to produce the final product. In a coextrusion process, a single operation is employed wherein different polymer melts or resins having vastly different properties are combined in a single production operation. In a cross-head extrusion process, one layer of the material is formed and thereafter, the additional layer or layers are applied in a subsequent extrusion operation.
Regardless of which process is employed, the resulting product comprises a plurality of layers integrally bonded to each other with each layer being formed from materials having either a different composition and/or a different density. In addition, other properties such as aesthetics, gas or vapor permeability, organoleptic barriers, printability, sealability, and the like constitute properties often imparted to one or more of the layers in order to provide a final product having particular characteristics.
In most applications, it has been found that cross-head extrusion is highly advantageous when vastly different types of material are to be combined together. Some applications benefitting from a cross-head extrusion process are for products such as plastic coated wires, protective or insulating coatings over metal or rigid materials. In addition, a foam layer peripherally surrounding a solid object or a solid layer peripherally surrounding a foam core are further examples benefitting from being produced by cross-head extrusion. In addition, the application of a more expensive or highly specific coating or layer, such as an antimicrobial layer or a corrosion resistent layer over a less expensive supporting substrate are further examples benefitting from cross-head extrusion processes.
Another area in which integrally bonded, multi-layer thermoplastic or elastomeric members have been extensively employed is for improving product safety in general and reducing injury to individuals due to unwanted or unexpected contact with the underlying product. In this regard, metal frames of products in support structures used by children, the elderly, the injured, or infirm individuals have received substantial attention and have been manufactured and/or improved by employing padding or cushioning protection in order to reduce or eliminate injuries that could result from contact.
Examples of such products are found in amusement parks and playgrounds and include slides, swing sets, moving vehicles, etc. In order to eliminate or reduce injuries, these products are now either manufactured with or retrofitted with padding or thermoplastic or elastomeric foam material to provide a soft, cushioned outer surface to otherwise hard surfaces or structures. In addition to the products detailed above, numerous other products such as race cars, baby furniture, bicycles, hospital beds, support posts for basketball, volleyball, and the like, gym equipment, boat fenders, etc. have all been manufactured with padding or thermoplastic or elastomeric foam constructions for added protection.
In addition, numerous products are manufactured with padded or cushioned outer surfaces for decorative purposes. These products include show booth displays, window displays, and the like. Furthermore, foam encapsulated products have also been commonly employed for insulating purposes, in order to conserve energy and reduce unwanted heat loss through various sources, such as hot water pipes which are exposed to substantially lower ambient temperatures.
In attempting to meet the demands for the products detailed above, foamed thermoplastic and/or elastomeric materials, such as polyethylene, have been accepted as the principal materials for meeting most product requirements. This acceptance has been caused by the ability of foamed thermoplastic and elastomeric to be formed in numerous sizes, shapes, and configurations. As a result, virtually any product can be effectively and efficiently improved by having the surface thereof covered by a soft, insulating, or cushioning member.
Although the products to be enhanced by incorporating an outer cushioned surface comprise a wide variety of sizes and shapes, elongated, cylindrically-shaped tubes typify the principal market for cushioned surfaces. Since elongated cylindrical tubes are used to manufacture posts, slides, railings, water pipes, swing sets, etc., it is readily apparent that such tube members form the principal market area wherein cushioning is desired.
As a result, elongated, longitudinally extending thermoplastic or elastomeric tubes formed from polyethylene foam material have been widely accepted and employed on numerous products for providing the desired soft, compressible, injury reducing surface thereto. Unfortunately, it has been found that these products have been unable to meet all of the demands imposed thereon.
One particular significant drawback that has occurred in these prior art uses, which has been incapable of being satisfactorily resolved, is the inability of these prior art elongated, thermoplastic or elastomeric tubes to withstand repeated abrasion, use, or contact. In general, although these prior art products do provide the desired soft, cushioning surface being sought, these prior art products are continuously receiving repeated contacting use in their installed position, and quickly degrade due to such use.
Prior art foam tubes are typically employed peripherally surrounding and protecting the hard outer surface of playground equipment found in retail outlets, such as food chains, as well as in swing sets employed at home. In order to protect the children playing on this equipment, the supporting frames and exposed metal surfaces are protected with thermoplastic or elastomeric cushioning means. However, during normal play, the children use this equipment continuously, kicking, rubbing, cutting, pulling, and tearing at the thermoplastic foam surfaces, causing such surfaces to be quickly degraded.
Another problem encountered in prior art installations is the inability of the thermoplastic or elastomeric components to withstand exposure from dirt, ink pens, and the like as well as exposure to pencils, crayons, and the like. As a result, in a relatively short time period, newly installed thermoplastic or elastomeric foam members become visually unappealing and unattractive.
In order to overcome these drawbacks, some prior art systems have attempted to peripherally envelope the thermoplastic or elastomeric foam tubes or members with a self-locking or self-sealing protective layer or sheet. Although the installation of such protecting sheets or layers have extended the life of the underlying thermoplastic or elastomeric tubes or members, the protecting sheets or layers are typically separated from the substrate they are protecting by the activities of the users and stripped from their surrounding position. As a result, the surfaces of the underlying thermoplastic or elastomeric members are quickly exposed to physical contact and surface degradation.
Therefore, it is a principal object of the present invention to provide a foamed, multi-layered, thermoplastic or elastomeric member/profile wherein the layers are integrally bonded to each other, providing a multi-layered product having precisely desired physical characteristics.
Another object of the present invention is to provide a foamed, multi-layered thermoplastic or elastomeric member/profile having the characteristic features described above which is capable of being quickly and easily mounted to any desired product to provide the desired physical attributes thereto.
Another object of the present invention is to provide a foamed, multi-layered thermoplastic or elastomeric member/profile having the characteristic features described which is producible in an elongated tubular or cylindrical form and is capable of being easily and quickly installed on any desired curved surfaced to provide a soft, cushioning protection thereto, while also eliminating product degradation or color discoloration during use.
Another object of the present invention is to provide a foamed, multi-layered thermoplastic or elastomeric member/profile having the characteristic features described wherein the outer layer is inherently scratch and puncture resistent, while also being capable of being easily cleaned to provide product longevity and long lasting visual appeal.
A further object of the present invention is to provide a foamed, multi-layered thermoplastic or elastomeric member/profile having the characteristic features described which is capable of being produced in virtually any desired color, configuration, surface treatment, and physical characteristics.
Another object of the present invention is to provide a foamed, multi-layered thermoplastic or elastomeric member/profile having the characteristic features described wherein each of the layers are integrally bonded to the adjacent layer, preventing unwanted removal or peeling of the layers from each other.
Another object of the present invention is to provide a foamed, multi-layered thermoplastic or elastomeric member/profile having the characteristic features described which incorporates layers that are water impermeable while also providing substantially increased resistance to degradation by contact with chemicals.
Another object of the present invention is to provide a foamed, multi-layered thermoplastic or elastomeric member/profile which is capable of being mass produced in any desired quantities, thereby providing a competitively priced product.
Other and more specific objects will in part be obvious and will in part appear hereinafter.